Chesterfield Water Hardness & Quality Report (2026)

Chesterfield, the Derbyshire market town in the Rother valley at the east Pennine edge, is supplied by Severn Trent Water. Supply draws from a combination of Pennine upland reservoir catchments — including the Ogston Reservoir in the Amber valley and the broader Severn Trent Derbyshire reservoir network — supplemented by groundwater from the Carboniferous Limestone formations of the Derbyshire Dales country to the west and south. The Rother catchment above Chesterfield drains both the Millstone Grit moorland of the eastern Pennines and the valley flanks where Carboniferous Limestone and Millstone Grit transition zones contribute harder groundwater and spring water. Water is treated at Severn Trent's Derbyshire facilities before distribution to Chesterfield and the north Derbyshire area.

Chesterfield's hardness of 167.5 mg/L (11.7°Clark) reflects its position at the Derbyshire Millstone Grit–Limestone interface. The Carboniferous Limestone of the Derbyshire White Peak — the famous plateau country of Dovedale and Monsal Dale — is a calcium-rich Dinantian limestone deposited approximately 340–345 million years ago, with groundwater dissolution producing moderately to very hard water in the limestone karst. The Rother catchment blend, incorporating this limestone influence alongside softer Millstone Grit moorland drainage, produces a supply in the lower moderately hard range of the Drinking Water Inspectorate (DWI) classification — harder than the direct Pennine-reservoir towns but softer than the chalk-belt cities.

Limescale requires regular household attention in Chesterfield. At 167.5 mg/L, limescale forms in kettles within three to four weeks and monthly descaling is advisable. Combi-boiler heat exchangers accumulate deposits at a moderate rate — annual servicing with a limescale check and an in-line scale inhibitor are recommended. Showerheads, taps, and bathroom surfaces develop regular deposits. Washing-up liquid lathers moderately. Maintaning a monthly descaling routine and using Calgon in the washing machine is standard practice for Chesterfield homes managing its moderately hard limestone-influenced supply.